Burner means for furnaces

ABSTRACT

A burner means for kilns including a burner orifice means for supplying fuel gas at a high velocity directed toward the furnace chamber, a combustion chamber aligned with the burner orifice means to receive the fuel gas and direct a high velocity stream into the furnace chamber, and a recirculation block mounted in the furnace wall at the downstream end of the combustion chamber. The recirculation block is provided with an axial passage through which the gases pass from the combustion chamber into the furnace chamber and a plurality of recirculation passages extending from the furnace chamber to an upstream portion of the axial passage so that gases recirculate from the furnace chamber for admixture with the gases directed into the kiln from the combustion chamber to thereby achieve a higher mass velocity of the gas stream entering the furnace chamber. The burner means may be provided with means for introducing diffusion air along two opposed jets which introduce the air downstream of the combustion chamber in an angled relation so that air flows along the axis of the burner in the direction of flow therethrough.

United States Patent [191 Remmey 1 Oct. 22, 1974 BURNER MEANS FOR FURNACES [75] Inventor: George Bickley Remmey,

Huntingdon Valley, Pa.

[52] US. Cl... 432/176, 431/351, 432/149 [51] Int. Cl. F23d 15/00 [58] Field of Search 432/176, 49, 26, 21, 196, 432/144, 145, 148-150, 24, 159, 161;

431/202, 174, DIG. 13, 351

Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen Attorney, Agent, or Firm-Smith, Harding, Earley &

Follmer [57] ABSTRACT A burner means for kilns including a burner orifice means for supplying fuel gas at a high velocity directed toward the furnace chamber, a combustion chamber aligned with the burner orifice means to receive the fuel gas and direct a high velocity stream into the furnace chamber, and a recirculation block mounted in the furnace wall at the downstream end of the combustion chamber. The recirculation block is provided with an axial passage through which the gases pass from the combustion chamber into the furnace chamber and a plurality of recirculation passages extending from the furnace chamber to an upstream portion of the axial passage so that gases recirculate from.the furnace chamber for admixture with the gases directed into the kiln from the combustion chamber to thereby achieve a higher mass velocity of the gas stream entering the furnace chamber. The

, burner means may be provided with means for introducing diffusion air along two opposed jets which introduce the air downstream of the combustion chamber in an angled relation so that air flows along the axis of the burner in the direction of flow therethrough.

17 Claims, 5 Drawing Figures [56] References Cited UNITED STATES PATENTS 2,289,629 7/1942 Cook 432/176 2,882,843 4/1959 Powell 431/D1G. 13 2,993,479 7/1961 Thurley 43l/DIG. 13 3,022,057 2/1962 Schmidt et a1 432/149 3,063,494 11/1962 Meyer 431/351 3,247,884 4/1966 McFadden et al 431/351 3,273,621 9/1966 Childree 431/351 3,424,542 1/1969 Hirschberg et a1, 431/348 3,614,074 10/1971 Wellford, Jr 432/176 3,620,513 11/1971 Wernicke 432/176 3,711,243 1/1973 Zink et a1. 431/351 FOREIGN PATENTS OR APPLICATIONS 1,028,113 5/1966 Great Britain 432/176 BURNER MEANS FOR FURNACES BACKGROUND OF, THE INVENTION Thisinvention relates to burner means for furnaces and, more particularly, to burner means for use in fur nac'es such as ceramic furnaces or kilns or metallurgical furnaces.

In kilns it is essential that the heating be controlled so that the ware may be heated from room temperature to red heat at a ratethat will not destroy the ware. It is also desirable that the temperature gradient within the ware be maintained as low as possible as the ware is heated. If the temperature at the surface of the ware is raised too rapidly, the high temperature gradient within the ware may result in defective ware. Also, it is desirable that the ware be heated uniformly throughout its surface area and that spot heating be avoided.

One burner meansdesigned to achieve the abovedescribed heating control in a kiln is shown in US. Pat. No. 3,055,652, in which arrangement air is admixed with'the fully burned products of combustion of the burners to thereby lower the temperature of the gas stream and increase its mass velocity. Hence, the harmful effect of excessive gas stream temperature isminimized and the ware is heated uniformly because the gas stream has added velocity to carry it across the furnace chamber before it begins to. rise. In US. Pat. No. 3,174,735 there is shown a burner means having an increased operating range which permits the operation of the kiln at extremely high temperatures where the fuel input demand is very high and, at the same time, operation of the kiln with controlled firing at very low temperatures without sacrificing control capability or temperature uniformity.

SUMMARY OF THE INVENTION locity than heretofore "and to achieve a higher mass velocity of the gas stream resulting in an increase in circulation and a greater throw across the kiln. Also, there is achieved a greater range of adjustability above the minimum operation level that will maintain circulation and throw across a kiln. Further, the burner means in accordance with the invention operates at greater efficiency and higher temperatures in the combustion chamber. Also the design is such that there will be a' longer life expectancy for the combustion chamber portion of the burner means. Further, there will be produced economies in construction, installation, repair and maintenance. Also, the construction is such as to be more leakproof even when operating at higher combustion chamber pressures. Other features of the invention will'be discussed more fully in the detailed description of theinvention.

Briefly stated, the b'umer means in accordance with the invention comprises a burner orifice means through which the fuel gases are delivered at a high velocity into a combustion chamber. The combustion chamber is encased in a metal supporting structure to provide a leakproof design permitting higher pressures and temperatures in the combustion chamber. From the combustion chamber, the gases are delivered through an axial passage in a recirculation block into the kiln chamber. The recirculation block is provided with a plurality of recirculation passages providing communication between the kiln chamber and the axial passage in the recirculation block. The'flow of gases from the combustion chamber through the axial passage in the recirculation block will cause a considerable volume of gases to be drawn from the kiln chamber through the recirculation passages. The high velocity jets used in conjunction with a recirculating block will entrain kiln gases through the venturi, thoroughly mix them with the gases leaving the combustion chamber, forming a jet of several times the mass. Of course, the additional weight of entrained gases will tend to slow the velocity of the jet as they add to the mass of the jet. The burner means is capable of developing jet velocities so high that the resultant velocity of the much heavier jet leaving the recirculation block is still as high as previous jet burners; Since so much more gas is forced into the furnace at high velocity, this invention develops very substantially greater mixing of all the gases in the furnace chamber. At the same time,the above conditions result .in decreasing the temperature difference between the gases and the ware being heated because of the dilution of the very hot gases coming from the combustion chamber by the entrained gases from the kiln. This prevents the extremely hot gases from contacting the ware being heated,-diminishing the possibility of hot spots or overheated areas more than any previous burner equipment.

Another advantage of this arrangement is the fuel economy that can be achieved by combusting the fuel and air atstoichiometric proportions which generates themaximum temperature and yields the highest fuel efficiency.

In accordance with another form of the invention, there is provided means for introducing diffusion air by means of two opposed jets 'which introduce the air downstream of the combustion chamber in an angled relation so that air flows along the axis of the burner means in the direction of flow therethrough. The design is such as to create a vacuum so that either operation of the burner or the diffusion air jets, or'the operation of both together, creates a vacuum for the recirculating gases. Accordingly, it is possible to'get good tempera- BRIEF DESCRIPTION OF Til-IE DRAWINGS FIG. 1 is a sectional view of a burner means in accordance with this invention incorporated in a furnace wall;

FIG. 2 is a view taken on line 2-2 of FIG. 3;

FIG. 3 is a view taken on line 3-3 of FIG. 1;

FIG. 4 is a view of a detail as viewed on line 4-4 of FIG. 3; and

FIG. 5 is a sectional view of another burner means in accordance with this invention incorporated in a furnace wall.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While the present invention as described below relates to gas-air burners, it will be noted that the same generalprinciples will apply to distillate oil fuel burners which would require means for atomizing the fuel oil prior to its mixture with the combustion air. The following description will be concerned with the gas-air type burner foruse in kilns which employ a plurality of the burner means and are generally mounted in the vertical walls of the kiln to direct their heating gas streams into the kiln chamber. It will be evident that the invention is applicable to burners which are located and arranged in other conventional ways.

Referring to the form of the invention shown in FIGS. 1 to 4, the burner means is mounted in the kiln vertical wall indicated generally at 10. This furnace wall is provided with suitable layers of refractory blocks in accordance with well known techniques of furnace construction. On the inside of the furnace wall 10 there is defined the furnace chamber 12. The furnace wall 10 is provided with a horizontally extending opening 13 adapted to receive the burner means that will be described hereafter, and comprising a bottom wall 14 and a pair of vertical side walls 16 and 18 which are relatively straight sided throughout the length of the wall. The top wall of the opening 13 has a portion 20 adjacent the furnace chamber 12 and a higher portion 22 outwardly-of portion 20 as is best shown in FIG. 1.

Means are provided for defining a combustion chamber for the burner means, such means being indicated generally at 24.'The combustion chamber means 24 comprises a generally cylindrical refractory portion 26 which defines centrally therein an axially extending combustion chamber 28 having a necked down portion 29 defining a restricted orifice at the downstream end thereof. Refractory portion 26 is encased by a high strength metallic cylindrical casing member 30. The metallic encasement of the refractory portion 26 serves to provide an air-tight, leakproof construction, which is necessary in' order that the burner means can operate at extremely high pressures and temperatures.

There is provided a burner orifice means 40 for supplying a high velocity stream of fuel gases and directing this high velocity stream axially into the combustion chamber 28 toward the furnace chamber 12. As is conventional, the burner orifice means 40 is provided with a pilot 42. Various types of burner orifice means may be utilized and the selection thereof will be apparent to those skilled in the art depending on the particular op erating conditions involved.

A recirculation block 50 is mounted at the downstream end of the combustion chamber means 24. Recirculation block 50 is made of a refractory material, i.e., a material, which may be either metal or nonmetal, capable of withstanding high temperatures without losing its mechanical or physical properties. Block 50 is generally rectangular in configuration and is adapted to fit within the rectangular opening provided ing passage 52 aligned with the axis of the burner orifice means 40 and the axis of combustion chamber 28 as is shown in FIG. 1. Passage 52 is shaped in a venturi configuration. By this arrangement, the combustion gases passing from combustion chamber 28 pass through passage 52 and into the furnace chamber 12.

Recirculation block 50 is provided with four recirculation'passages 54 located in the corners of the block 50 as is'best shown in FIG. 3. As shown in FIG. 4 wherein a section of the block 50 is illustrated, the passages 54 communicate at one end with the inlet portion of the venturi passage 52 and extend in a smooth configuration radially outwardly and then axially to the end 56 of recirculation block 50 adjacent furnace chamber 12. The passages 54 communicate with the furnace chamber 12 at ports in the corners of the block 50 formed partially by an arcuate cutout 58. I

It will be apparent that the high velocity gas stream passing from the combustion chamber 28 axially through the venturi passage 52 to the furnace chamber 12 will draw gases from the furnace chamber 12 through the recirculating passages by a venturi-like action. These recirculated gases combine with the high velocity gas stream from the combustion chamber to increase substantially the mass velocity of the gas stream entering the furnace chamber 12. In accordance with the invention the parts are designed so that the high velocity gas stream passing from the combustion chamber is preferably of the order of around 500 to 550 miles per hour, although velocities of the order of 400 miles per hour may be used. With velocities at this order, the recirculation block is able to entrain gases in amounts much higher than previous burner means. As discussed above, the recirculation block entrains recirculating gases to form a jet of several times the mass.

In the operation of the burner means shown in FIGS. 1 to 4, the burner orifice means 40 will direct a high velocity fuel gas stream axially onto the combustion chamber 28 where combustion will take place. The fully combusted gases will then pass axially from the combustion chamber 28 and through the venturi passage 52 onto the furnace chamber 12. All this occurs at an extremely high velocity. This gas stream will draw recirculating gases from the furnace chamber 12 through the recirculating passages 54, these recirculating gases combining with the combustion gases to pass through the venturi passage 52 back into the furnace chamber 12. It will be apparent that the burner means in accordance with the invention will achieve an extremely high mass velocity of the gas stream which is delivered into the furnace chamber resulting in an increase in circulation and a greater throw across the kiln. Moreover, by reason of the metal encasement and the ventilated mounting of the combustion chamber means, the burner means can operate at extremely high pressures and temperatures without heat leaking out to cause damage to adjacent walls.

In FIG. 5 there is shown another form of burner means in accordance with the invention which comprises many elements which are essentially identical to that shown in FIGS. 1 to 4 wherefore corresponding parts have been given like reference numerals with primes added. FIG. 5 is a sectional view in plan similar to that shown in FIG. 2. The burner means is mounted in the kiln vertical wall 10 which defines on its inside the furnace chamber 12'. The burner means is mounted in an opening 13' in the furnace wall 10', said opening comprising a bottom wall 14 and a pair of side walls 16' and 18.

There is provided a combustion chamber means 24' having a refractory portion 26 which defines a combustion chamber 28 having a portion 29' defining a restricted orifice. Refractory portion 26 is encased in a metallic casing member 30. The combustion chamber means 24' is mounted in the opening 13' of the furnace wall by the same type of mounting arrangement shown in FIGS. 1 to 4.

There is provided a burner orifice means 40' identical to the burner orifice means 40 for the burner means shown in FIGS. 1 to 4; There is also provided a recirculation block 50' which is identical to the recirculation block 50 shown in the burner means of FIGS. 1 to 4,

such recirculation block 50 being provided with recirculation passages which communicate at the upstream end of an axially extending venturi passage 52 at the location whereat a cylindrical inlet chamber 53 is formed. As in the burner means of FIGS. 1 to 4, the combustion gases pass from the combustion chamber 28 through the passage 52' into, the furnace chamber 12' and serve to draw gases from the furnace chamber 12' through the recirculation passages.

The added feature of the form of the invention'shown in FIG. 5 is the provision of means for introducing diffusion air into the burner means by means of two opposed jets which introduce the air downstream of the combustion chamber 28' in an angled relation to the axis of the burner means so that air flows along the axis of the flowing gases. Such means comprises a pair of tubes 70 embedded in a pair of corresponding bores in refractory portion 26', such tubes extending in the angled relation shown in FIG. 5. Adjacent the' downstream end of the tubes 70, there is provided ports 74 at the downstream end of the refractory portion 26'. These ports 74 provide communication with the inlet chamber 53' at the upstream end of the venturi passage 52. The tubes are arranged to be in diametrically opposed relation and at an angleto the axis of the burner so as to direct an air stream into the venturi passage 52' so that the air flows. along the axis of the burner.

Means are provided for supplying air under pressure tothe upstream end of the tubes 70. Such means comprises a suitable supply of air under pressure 76 which is connected. to the upstream endof apair of conduits 78 which are communicated at their downstream end with the tubes 70 as shown in FIG. 5. There may be provided suitable sealing means 80 at the connection between tube 70 and conduits 78. The air supply 76 is provided with suitable control means 77 for varying the flow of air supplied to the conduits 78 from no flow to a predetermined maximum flow.

In the operation of the burner means shown in FIG. 5, the burner orifice means 40' directs a high velocity fuel gas stream axially into the combustion chamber 28' where combustion takes place. The combustion gases are then passed axially from the restricted orifice of chamber 28' through the venturi passage 52' into the furnace chamber 12' at a high velocity. This gas stream draws recirculating gases from the furnace chamber 12' through the recirculation passages in recirculation block 50', these recirculating gases combining with the combustion gases for passage through venturi passage 52' into the furnace chamber 12'. In addition, diffusion air is introduced into the upstream end of passage 52' at the inlet chamber 53' as desired in accordance with theoperation of the burner means. The diffusion air serves to reduce the temperature of the gases entering the kiln chamber and to increase the mass velocity thereof. It will be noted that the burner means will produce a vacuum condition at the downstream of the diffusion air means, namely in chamber 53' adjacent the ports 74. This vacuum is produced by the action of the combustion gases flowing from chamber 28 through passage 52'. In addition, a vacuum condition is also produced at the location in inlet chamber 53' where the recirculating gases pass into the venturi passage 52' by the action of the diffusion air jets flowing from tube through inlet chamber 53 and into the venturi passage 52'. Thus, a vacuum condition is produced at the end of the recirculating passages in the region of the inlet chamber 53 by operation of either the burner means directing combustion products from chamber 28 into venturi passage 52' or by operation of the diffusion air means directing air under pressure from tubes 70 into the venturi passage 52'. Because of the arrangement described above, chamber 53' is always under a vacuum. The level of this vacuum depends on the velocity from the burner. However, by reason of the arrangement of the diffusion air tubes 74, the flow of diffusion air can also develop a vacuum in chamber 53' since the junction of the flow from the two diffusion air tubes results in a combined flow continuing along the axis of the venturi in the recirculation block. In the case of periodic kilns which must be heated very slowly in the early and later stages of the firing cycle, this arrangement offers a very substantial improvement over previously used-equipment.

Moreover, in the previous designs, a change in flow of the diffusion air would cause a pressure change in the combustion chamber which would affect the flow and ratio of the gases entering the combustion chamber. Also a change in the level of operation of the combustion chamber would affect the flow of diffusion air, complicating the control equipment and resulting in a situation that often departed from the most efficient utilization of fuel. Since it has been proven that jet firing has distinct advantages it is desirable to use jet firing even when the kilns are used for reduction firing where excess air or 0 must not be in the furnace atmosphere. Other bumers employing diffusion air or excess air cannot develop a good degree of temperature uniformity because the excess air that is necessary with that type of burner cannot be used. However, in the arrangement shown in FIG. 5 with the diffusion air turned off, the velocity from the combustion chamber will entrain enough additional gases from the kiln to give sufficient mass velocity needed for good firing under reducing conditions. Obviously the reducing atmosphere is maintained in the kiln because the additional gases necessary to increase the force of the jets comes from the kiln where all the oxygen has been converted to CO and H20.

For periodic firing, the arrangement in FIG. 5 is used which enables the kiln to be controlled at very low temperatures with the use of air moving through the diffusion air tubes to develop the necessary jet circulation when it is necessary to keep the combustion gases at minimum levels. At the high temperatures where reduction firing is done, sufficient fuel can be used to maintain satisfactory jetlevels without the use of air through the diffusion air tubes.

It will be apparent that changes may be made in the construction and arrangement of parts without departing from the scope of the invention. For example, the burner means of FIG. 5 may be provided with more than two opposed jets for introducing diffusion air.

I claim:

ing a furnace chamber comprising burner orifice means for supplying fuel at a high velocity directed toward the furnace I chamber, means providing a combustion chamber aligned with said burner orifice means to receive said fuel and direct a high velocity stream along a straight path a substantial distance into the furnace chamber, and a recirculation means in the furnace wall at the downstream end of said combustion chamber, said recirculation means having an axial passage through which said high velocity stream from said combustion chamber passes as it moves to the furnace chamber, and recirculation passage means extending from communication with the furnace chamber to an upstream portion of said axial passage and being constructed and arranged so that the high velocity stream passing through said axial passage causes gases to be drawn from the furnace chamber through said recirculation passage means to the upstream end of said axial passage whereat said gases join said high velocity stream and recirculate into the furnace chamber.

2. Burner means according to claim 1 wherein said recirculation means comprises a recirculation block of refractory material mounted in the furnace wall, and including means defining an opening in said furnace wall for securely receiving said recirculation block, said recirculation passage means including passages located .at the peripherally spaced regions of said recirculation leakproof metallic casing extending around the exterior of said refractory portion 5. Burner means according to claim 3 wherein said combustion chamber means is formed by a refractory portion which defines said combustion chamber and a metal casing extending around the exterior of said refractory portion for strengthening the same, and including means for mounting said combustion chamber means in an enlarged opening within the furnacewall so that said combustion chamber means is spaced from the furnace wall to provide for ventilation thereof.

6. Burner means according to claim 2 wherein said recirculation block is generally rectangular in configuration and said passages are located at the comers thereof.

7. Burner means according to claim 1 wherein said burner orifice means and said combustion chamber are constructed and arranged so that the velocity of the high velocity stream directed from said combustion chamber into said furnace chamber is greater than 400 miles per hour.

8. Burner means according to claim 7 wherein the velocity of said high velocity stream from said combustion chamber is around 500 to 550 miles per hour.

9. A burner means for a furnace having a wall defining a furnacev ware heating chamber comprising burner orifice means for supplying fuel at a high velocity directed toward the furnace chamber along a burner axis, means providing a combustion chamber aligned with said burner orifice means to receive said fuel and direct a high velocity gas stream of combustion products along the burner axis a substantial distance into the furnace ware heating chamber, and means for introducing diffusion air into said combustion gas stream along at least two opposed jets arranged in an acute angle with respect to the high velocity flow along the burner axis to direct the flow of air toward the burner axis in opposed relation and along the direction of flow of said combustion gas stream.

l0. Burner means according to claim 9 including block means mounted in the furnace wall at the downstream end of said combustion chamber and having an axial passage through which said combustion gas stream passes from said combustion chamber as it moves to the furnace chamber.

11. Burner means according to claim 10 wherein said diffusion air introducing means comprises a pair of tubes arranged in diametrically opposed relation.

12. Burner means according to claim 10 wherein said block means includes a plurality of recirculation passages extending from communication with the furnace chamber to an upstream portion of said axial passage whereby the gas stream passing through said axial passage causes gases to be drawn from the furnace chamber through said recirculation passages to the upstream end of said axial passage whereat said gases join said gas stream and recirculate into said furnace chamber.

13. A burner means according to claim 12 wherein said diffusion air introducing means are arranged to introduce said diffusion air into said axial passage at a location adjacent the upstream portion of said axial passage whereat said recirculation passages communicate with said axial passage for producing a vacuum condition at the end of said recirculation passages for drawing gases therethrough.

l4. Burner means according to claim 1'3 wherein said combustion chamber means is formed by a refractory portion which defines said combustion chamber and a metal casing extending around the exterior of said refractory portion for strengthening the same, and including means for mounting said combustion chamber means in an enlarged opening within the furnace wall so that said combustion chamber means is spaced from the furnace wall to provide for ventilation thereof.

15. Burner means for a furnace having a wall for defining a furnace chamber comprising burner orifice means for supplying fuel at a high velocity directed toward the furnace chamber, means providing a combustion chamber aligned with said burner orifice means to receive said fuel and direct a high velocity stream along a straight path a substantial distance into the furnace chamber, and a block mounted in the furnace wall at the downstream end of said combustion chamber, said block having an axial passage through which said high velocity stream from said combustion chamber passes as it moves to the furnace chamber, said combustion chamber means being formed by a refractory portion which defines said combustion chamber and a leakproof metallic casing extending around the exterior of said refractory portion, said burner orifice means and said combustion chamber being constructed and arranged so that the velocity of the high velocity stream directed from said combustion chamber into said furnace chamber is greater than 400 miles per hour.

16. Burner means according to claim 15 including means for mounting said combustion chamber means in an enlarged openingwithin the furnace wall so that said combustion chamber means is spaced from the furnace wall to provide for ventilation thereof.

17. Burner means according to claim 15 wherein the velocity of said high velocity stream from said combustion chamber is around 500 to 550 miles per hour. 

1. Burner means for a furnace having a wall for defining a furnace chamber comprising burner orifice means for supplying fuel at a high velocity directed toward the furnace chamber, means providing a combustion chamber aligned with said burner orifice means to receive said fuel and direct a high velocity stream along a straight path a substantial distance into the furnace chamber, and a recirculation means in the furnace wall at the downstream end of said combustion chamber, said recirculation means having an axial passage through which said high velocity stream from said combustion chamber passes as it moves to the furnace chamber, and recirculation passage means extending from communication with the furnace chamber to an upstream portion of said axial passage and being constructed and arranged so that the high velocity stream passing through said axial passage causes gases to be drawn from the furnace chamber through said recirculation passage means to the upstream end of said axial passage whereat said gases join said high velocity stream and recirculate into the furnace chamber.
 2. Burner means according to claim 1 wherein said recirculation means comprises a recirculation block of refractory material mounted in the furnace wall, and including means defining an opening in said furnace wall for securely receiving said recirculation block, said recirculation passage means including passages located at the peripherally spaced regions of said recirculation block and being formed in said block to provide smooth flow passages for the recirculating gases.
 3. A burner means according to claim 2 wherein said axial passage has a venturi shape, said recirculation passages being arranged to communicate with the inlet portion of the venturi.
 4. Burner means according to claim 1 wherein said combustion chamber means is formed by a refractory portion which defines said combustion chamber and a leakproof metallic casing extending around the exterior of said refractory portion.
 5. Burner means according to claim 3 wherein said combustion chamber means is formed by a refractory portion which defines said combustion chamber and a metal casing extending around the exterior of said refractory portion for strengthening the same, and including means for mounting said combustion chamber means in an enlarged opening within the furnace wall so that said combustion chamber means is spaced from the furnace wall to provide for ventilation thereof.
 6. Burner means according to claim 2 wherein said recirculation block is generally rectangular in configuration and said passages are located at the corners thereof.
 7. Burner means according to claim 1 wherein said burner orifice means and said combustion chamber are constructed and arranged so that the velocity of the high velocity stream directed from said combustion chamber into said furnace chamber is greater than 400 miles per hour.
 8. Burner means according to claim 7 wherein the velocity of said high velocity stream from said combustion chamber is around 500 to 550 miles per hour.
 9. A burner means for a furnace having a wall defining a furnace ware heating chamber comprising burner orifice means for supplying fuel at a high velocity directed toward the furnace chamber along a burner axis, means providing a combustion chamber aligned with said burner orifice means to receive said fuel and direct a high velocity gas stream of combustion products along the burner axis a substantial distance into the furnace ware heating chamber, and means for introducing diffusion air into said combustion gas stream along at least two opposed jets arranged in an acute angle with respect to the high velocity flow along the burner axis to direct the flow of air toward the burner axis in opposed relation and along the direction of flow of said combustion gas stream.
 10. Burner means according to claim 9 including block means mounted in the furnace wall at the downstream end of said combustion chamber and having an axial passage through which said combustion gas stream passes from said combustion chamber as it moves to the furnace chamber.
 11. Burner means according to claim 10 wherein said diffusion air introducing means comprises a pair of tubes arranged in diametrically opposed relation.
 12. Burner means according to claim 10 wherein said block means includes a plurality of recirculation passages extending from communication with the furnace chamber to an upstream portion of said axial passage whereby the gas stream passing through said axial passage causes gases to be drawn from the furnace chamber through said recirculation passages to the upstream end of said axial passage whereat said gases join said gas stream and recirculate into said furnace chamber.
 13. A burner means according to claim 12 wherein said diffusion air introducing means are arranged to introduce said diffusion air into said axial passage at a location adjacent the upstream portion of said axial passage whereat said recirculation passages communicate with said axial passage for producing a vacuum condition at the end of said recirculation passages for drawing gases therethrough.
 14. Burner means according to claim 13 wherein said combustion chamber means is formed by a refRactory portion which defines said combustion chamber and a metal casing extending around the exterior of said refractory portion for strengthening the same, and including means for mounting said combustion chamber means in an enlarged opening within the furnace wall so that said combustion chamber means is spaced from the furnace wall to provide for ventilation thereof.
 15. Burner means for a furnace having a wall for defining a furnace chamber comprising burner orifice means for supplying fuel at a high velocity directed toward the furnace chamber, means providing a combustion chamber aligned with said burner orifice means to receive said fuel and direct a high velocity stream along a straight path a substantial distance into the furnace chamber, and a block mounted in the furnace wall at the downstream end of said combustion chamber, said block having an axial passage through which said high velocity stream from said combustion chamber passes as it moves to the furnace chamber, said combustion chamber means being formed by a refractory portion which defines said combustion chamber and a leakproof metallic casing extending around the exterior of said refractory portion, said burner orifice means and said combustion chamber being constructed and arranged so that the velocity of the high velocity stream directed from said combustion chamber into said furnace chamber is greater than 400 miles per hour.
 16. Burner means according to claim 15 including means for mounting said combustion chamber means in an enlarged opening within the furnace wall so that said combustion chamber means is spaced from the furnace wall to provide for ventilation thereof.
 17. Burner means according to claim 15 wherein the velocity of said high velocity stream from said combustion chamber is around 500 to 550 miles per hour. 